A control under which a driving or braking torque is suppressed and converged if wheels of a train Slip/skid, and the torque is returned to an original one if the slip/skid is converged is called “readhesion control”. There is the readhesion control using an adhesion torque which is a maximum value of the tangential force coefficient, and corresponds to an adhesion coefficient determined according to environmental conditions between the wheels and rails. The related art is disclosed in Japanese Unexamined Patent Application Publication No. Hei-1(1989)-243803. Regarding a value returning the torque, in the disclosure of this publication, “the adhesion coefficient is always calculated, and at the same time, a motor current corresponding to a torque generated in an electric motor, which is calculated by the generated torque calculation unit, is calculated in advance. When slip/skid is detected by the slip/skid detection unit, the motor current corresponding to the maximum or substantially maximum adhesion coefficient is calculated according to the adhesion coefficients before and immediately after slip/skid occurs, and the motor current corresponding to the torque generated in the electric motor. The motor current is supplied as a current command of the electric motor.” The related art is also disclosed in Japanese Unexamined Patent Application Publication No. 2000-125406. In the disclosure of this publication, “when the adhesion coefficient drastically fluctuates, a speed detection delay of a main electric motor develops into large slip and skid. In order to produce readhesion, the torque must be largely reduced, thereby leading to the deterioration of a ride quality, and a reduction in the utilization ratio of the adhesion force. A torque command value of the main electric motor is controlled while the tangential force and the tangential force coefficient are momentarily estimated by a minimal-order disturbance observer according to an estimated speed small in delay using voltage and current information of the main electric motor with high precision and promptly (refer to abstract of the publication).